1. Field of the Invention
The present invention generally relates to an inkjet printing system, and in particular to a suction apparatus which is used to clean an inkjet head.
2. Description of the Related Art
In general, an inkjet printing system is equipped with an ink suction apparatus which draws ink sludge within ink nozzles and bubbles trapped in an ink supply system by applying a suction force. Such a suction operation is periodically performed to avoid the deterioration of print quality.
A conventional suction pump has been disclosed in Japanese Patent Unexamined Publication No. 4-37557. The suction pump is provided with a piston performing a reciprocating motion in an inner cylinder and a piston valve which performs a reciprocating motion depending on the piston in a cylindrical space between the inner cylinder and an outer cylinder. The suction pump is further provided with an open/close valve and a pressure reducing means which is a space formed by the piston, open/close valve, and the open/close valve, the space varying in volume depending on the reciprocating motion of the piston. In other words, the pressure reducing means is arranged between the piston valve and the open/close valve. In the conventional suction pump like this, air is forced out of the pressure reducing means by pushing up the piston with the open/close valve closed and the piston valve open, and then a suction force is generated by pulling down the piston with the open/close valve open and the piston valve close.
However, the conventional suction pump needs the piston valve and the open/close valve in addition to the pressure reducing means, resulting in the increased number of parts and the complicated mechanism. This causes the increased weight and further the increased cost of the pump.